The P77C292MM adapter has a further dimension that effects the operating window. The V
term
setting influences the
dynamic range. A plot of V
term
and valid input voltages is shown in the Overload Specification section.
Improving measurement accuracy
DSP correction filtering
TDP7700 Series probes and probe tips use DSP correction filtering to optimize probe measurement fidelity. High frequency
time domain measurement performance characteristics such as rise time, aberrations, and pulse flatness are improved by
DSP correction filtering. Similarly, frequency domain performance characteristics such as bandwidth, frequency response
flatness, and differential signal coupling are improved by DSP correction filtering. DSP correction filtering is performed
automatically by the oscilloscope using S-parameter characterization data downloaded from probe and probe tip storage
memories. This S-parameter data is unique for each probe and probe tip, rather than the nominal response data that was
used in some previous generation probe families.
Distinct S-parameter data sets are stored in probe memory for each probe input mode and step gain setting combination.
Every different input mode and step gain combination has a slightly different amplifier signal path, which requires different
signal response correction. Since the solder tip buffers do not have complex mode switching, only one S-parameter data set
is stored in the probe tip storage memory. The high frequency signal performance of the P77BRWSR browser tip changes
slightly as the tip spacing is adjusted. Several S-parameter data sets are stored in the browser tip memory and
automatically switched to the optimum data set, under control of the browser tip spacing position detection circuitry.
S-parameter characterization data are measured for each probe and probe tip as part of the manufacturing test process.
TDP7700 Series probe signal performance is measured using a 3-port VNA measurement configuration with a 2-port
TekFlex connector input and a 1-port TekVPI interface output. Custom test fixtures have been developed for making VNA
port connections to the probe TekFlex connector input and TekVPI interface output. Test fixtures designed for connecting to
the probe input and output signal ports are de-embedded to remove interconnect losses and signal path imperfections.
TekFlex probe tip signal performance is measured using a 4-port VNA measurement configuration with 2-port input and
output connections. Because the TekFlex probe tips do not have standard RF connectors at their inputs or outputs, the
custom test fixtures inject and receive VNA port signals. Custom calibration standards were developed to support de-
embedding these probe tip manufacturing test fixtures.
Solder-in tip connection wire length
There are four via locations for soldering wire connections between the probe tip and the measurement DUT.
The via connections include the probe tip A and B inputs for a differential signal and two ground connections for best
performance and flexibility in connecting to a close DUT ground. In general, the probe tip soldered wire connection length
should be kept as short as possible. In addition, the probe tip A and B input wires should be matched in length for best
differential mode measurement performance.
The differential input mode does not require a ground reference wire connection, since the differential measurement
process provides its own virtual ground. The single-ended input modes, which include A-GND mode, B-GND mode, and
common mode, all require at least one ground wire connection.
While only connecting the differential inputs of the probe is required and is most convenient, if there is room for another
connection and a circuit ground near the probe tip, connecting to a ground connection is recommended. Connecting the
ground can help avoid a situation where a large potential on the ground of the DUT causes the test signal to drift outside of
the linear range of the input amplifier of the probe. Ideally, it is a good idea to connect the differential inputs and the ground
to avoid clipping of the signal in the probe amplifier.
The measurement performance of all input modes is affected by the length of the input wire connection, with high frequency
performance degradation increasing with increased wire length.
The measurement performance of the single-ended input modes is affected by the length of the ground wire connection,
with high frequency performance degradation also increasing with increased ground wire length. The TekFlex solder-in
Theory of operation
TDP7700 Series TriMode™ Probes Technical Reference
14
